smaller right CAF. Color Doppler imaging enhanced the findings of the left CAF by simultaneously displaying blood flow in the fistulous tract and the right ventricle. Although we were able to visualize the proximal dilated right coronary artery by TTE, no abnormal flow pattern could beobtained with the Doppler technique. Technical difficulties with resolution, gain settings, angulation of the jet flo~ failure to image the vessel in the moving heart, and absence of adequate acoustic windows are some of the problems that have been encountered in the TTE examinations. 5 In this regard, our case study illustrates enhanced identification of the smaller right CAF by TEE. Because of better resolution and fewer impediments to ultrasound transmission, TEE appreciably complements the TTE examination, particularly the atria, atrial septum, or atrioventricular valves." In the literature, 1.2 TEE was shown to better define the complete course of the fistula and to map the flow than TTE in two cases with the drainage site in the right atrium. Hence, it did not appear surprising that TEE demonstrated the right CAF at the lateral aspect of the right atrium better than TTE did, although TEE also failed to depict the drainage site in the right ventricle. Transesophageal echocardiography with color Doppler imaging still could not reveal an abnormal jet in the right fistula, presumably because the flow was perpendicular to the ultrasound beam. The limited utility of TEE in evaluating a left circumflex coronary artery-right ventricle fistula is well demonstrated in this patient. Monoplanar TEE is limited in the scanning plane and also has difficulty in imaging extreme anterior or posterior structures." In this case study the drainage sites of both fistulas were in the posterior wall of the right ventricle distal to the insertions of both papillary muscles, quite close to the apex, which is extremely anterior in location. No wonder that TEE could not define the drainage sites clearly. In fact, TEE and TTE are complementary to each other, rather than competitive. Further studies with different patterns of CAF examined by both TTE and TEE should be extended before we can draw more definite conclusions in terms of relative merits and limitations of these two diagnostic modalities. REFERENCES

2

3

4

5

6

Kuo cr; Chiang C~ Fang BR, Lee C~ Hsu TS, Lee YS, et al. Coronary artery fistula: diagnosis by transesophageal twa-dimensional and Doppler echocardiography. Am Heart J 1992; 123:21820 Calafiore PA, Raymond R, Schiavone WA, Rosenkranz ER. Precise evaluation of a complex coronary arteriovenous fistula: the utility of transesophageal color Doppler. J Am Soc Echo 1989; 2:337-41 Nishiguchi T, Matsuoka Y, Senneri E, Okishima T, Suzumiya H, Akimoto K, et aI. Congenital coronary artery fistula: diagnosis by two-dimensional Doppler echocardiography. Am Heart J 1990; 120:1244-48 Trask JL, Bell A, Usher BW Doppler color Row imaging in detection and mapping of left coronary artery fistula to right ventricle and atrium. J Am Soc Echo 1990; 3:131-34 Velvis H, Schmidt KG, Silverman NH, Turley K. Diagnosis of coronary artery fistula by two-dimensional echocardiography, pulsed Doppler ultrasound and color Row imaging. J Am Coli Cardiol 1989; 14:968-76 Nanda xc. Pinheiro L, Sanyal RS, Storey O. Transesophageal biplane echocardiographic imaging: technique, planes, and clinical usefulness. Echocardiography 1990; 7:771-88

Positive Pressure Mechanical Ventilation Augments Left Ventricular Function in Acute Mitral Regurgitation* Shawn E. Wright, M.D.; and john E. Heffner, M.D., F.C.C.~

Although inconclusively established, positive pressure ventilation may augment cardiac function in congestive cardiomyopathies. We report a patient with acute mitral regurgitation who experienced enhanced myocardial performance and resolution of large pulmonary artery v waves during mechanical ventilation. This observation supports the existence of a cardiac booster effect from positive pressure ventilation. (Chest 1992; 102:1625-27)

co = cardiac output; PCWP = pulmonary capillary wedge pressure; PEEP

=positive end-exiratory pressure

A lthough usually associated with reduction of cardiac 1'1. output, positive pressure ventilation in patients with depressed left ventricular function and volume overload may augment cardiac performance and improve systemic hemodynamics.':' The mechanisms underlying this cardiac "booster" effect of mechanical ventilation, however, remain controversial." We report a patient with a myocardial infarction and acute mitral insufficiency who required positive pressure ventilation for the management of pulmonary edema. The presence of large v waves noted with pulmonary capillary wedge pressure (PCWP) monitoring and the patient's sudden self-extubation provided a unique opportunity to observe the effects of positive pressure ventilation on left ventricular function. CASE REPORT A 78-year-old man with chronic atrial fibrillation and hypertension

was admitted to the hospital because of chest pain and electrocardiographic evidence of an acute, lateral wall myocardial infarction. Lung fields were clear to auscultation and a wade 1/6 murmur of mitral regurgitation was heard. A chest roentgenogram showed cardiomegaly and mild pulmonary edema. The pain responded to morphine sulfate, nitroglycerine, and labetalol. On the second hospital day, myocardial fractions of creatinine phosphokinase were elevated (11.7 percent of2,205 lUlL). An echocardiogram confirmed moderate to severe mitral insufficiency, left atrial enlargement, and left ventricular wall hypokinesia. Captopril therapy, 6.25 mg every 8 h by mouth, was started. On the third day, progressive dyspnea and hypoxia (Pa02 of 77 mm Hg on 100 percent face mask OJ developed. A chest roentgenogram revealed worsening pulmonary edema, and a repeat echocardiogram demonstrated severely impaired lateral wall motion, reduced ejection fraction, and severe mitral insufficiency. Treatment with intravenous diuretics, nitroprusside (6.3 JA,Wkw'min), and dopamine (3 JA,glkglmin) was begun after discontinuation of treatment with oral nitrates and labetalol. Placement of a Row-directed pulmonary artery catheter on the fourth hospital day revealed a central venous pressure of 10 mm Hg, PCWP of 21 mm Hg, and pulmonary artery v waves measuring 55 mm Hg (Fig 1, upper). *From the Department of Medicine, St. Joseph's Hospital and Medical Center, Phoenix. Reprint requests: Dr. Heffner, St. Josephs Hospital and Medical Center, Phoenix 85001-2071 CHEST I 102 I 5 I NOVEMBER, 1992

1625

f -,l.-'l

l

IM·)-

. J\

f\..